Chimie biologique Physique 4ème sem 2006

CONTENT

1. PROTEIN STRUCTURE AND FUNCTION

2. EXPLORING PROTEINS

3. DNA, RNA & FLOW OF GENETIC INFORMATION

4. EXPLORING GENES

5. ENZYMES : BASIC CONCEPTS AND KINETICS

6. PORTRAIT OF AN ALLOSTERIC PROTEIN ch 10

7. MEMBRANE STRUCTURE AND DYNAMICS

8. MEMBRANE CHANNELS AND PUMPS

9. SIGNAL TRANSDUCTION

10. MOLECULAR MACHINES & PROTEIN DESIGN

11. ANTIBODIES AND T-CELL RECEPTORS

Portrait of an allosteric protein: Hemoglobin

chapter 10, Stryer

Allosteric enzymes

Do not obey Michaelis-Menten kinetics

Contain multiple subunits & multiple

active sites

Binding of substrate to one active site

affects properties of other active sites in

same enzyme molecule

Cooperativity: Binding of substrate to

one active site facilitates binding to others

Regulation of metabolic pathways:

Activity of allosteric enzymes are

adjusted for needs of cell

3D structure of myoglobinKendrew 1957

Scheme of helices &

heme group

Distribution of amino acids in myoglobin

Hydrophobic (yellow) Charged (blue) Others (white)

Details of oxygen binding site in myoglobin

!2"2 tetramer of human hemoglobinPerutz 1959 (started 1936)

Hemoglobin transports oxygen efficiently by cooperative binding

Oxygen binding markedly changes the quaternary structure

of hemoglobin

O2

Position of iron in deoxyhemoglobin

Oxygen binding induces structural changes

Conformational changes in hemoglobin induced by oxygen binding

Hemoglobin transports oxygen efficiently by cooperative binding